Various manufacturing processes are known which require a vacuum environment (pressures less than atmospheric pressure). Vacuum environments are useful in manufacturing printed circuit boards with multiple layers adhesively attached to one another. The vacuum environment facilitates removal of air, or air and moisture, from between the layers.
Vacuum environments are also useful in manufacturing laminate structures of composite materials, such as for use in manufacturing aircraft. Glass laminate structures also may be assembled in a vacuum environment. Thermal molding, where a polymeric layer is heated and shaped around a mold, may also be performed in a vacuum environment.
In manufacturing the above products and other products, it is often important to provide an appropriate vacuum environment to facilitate removal of air, or air and moisture, between the layers of material in the product to be manufactured. Heat and/or external force may be applied to facilitate manufacture.
Apparatus are known for creating a vacuum environment. One example of a known vacuum apparatus includes an arrangement with a flexible top sheet and a flexible bottom sheet adhesively bonded together with caulk. A product for exposure to the vacuum environment is placed between the top and bottom sheets prior to completely closing the arrangement with the caulk. A valve permits withdrawal of air, or air and moisture, from the enclosed chamber between top and bottom sheets. Vacuum arrangements of this type are sometimes referred to as "turkey bags".
Various problems exist with the above vacuum arrangement. One problem is that the arrangement is not reusable. Further, setup prior to forming the vacuum environment is often difficult and time consuming since the top sheet and the bottom sheet must be adhesively caulked together. Sometimes caulk particles are drawn into the valve during use, causing problems with the vacuum supply. Another problem with the arrangement is that stacking of multiple arrangements for simultaneous manufacture is difficult, or impossible, due to the location of the valve through one of the flexible sheets, and a lack of rigidity of the structure. Sometimes the flexible sheets are very thin and are subject to being easily punctured.
Another example of a known vacuum apparatus includes an arrangement with a metal top plate and a metal bottom plate. A seal arrangement, including at least one flexible seal, is positioned between the top and bottom plates to form an enclosed chamber. A product to be exposed to the vacuum environment is placed within the enclosed chamber between the top and bottom plates and the seal arrangement. A valve is provided to withdraw air, or air and moisture, from the enclosed chamber. Vacuum arrangements of this type are sometimes referred to as "vacuum frame assemblies".
Since the second type of vacuum arrangement includes rigid top and bottom plates, neither structure can conform to a non-parallel surface on the product. If an external compressive force is to be applied to the exterior of the top and bottom plates to facilitate manufacturing through mechanical assistance, the height of the seal arrangement is critical relative to the size of product. In addition, the flexible seals must be replaced after a period of time due to fatigue, since typical usage produces significant deformation of the seal structure.
In the art of manufacturing processes involving vacuum environments, cost of materials comprising the vacuum apparatus is important. Ease of setup and time to setup the vacuum apparatus are also important concerns. Reliability, such as the ability to consistently permit formation of the proper vacuum environment, and the ability to reduce waste of products processed with the vacuum apparatus, are further concerns. In addition, reducing the amount of disposable elements comprising the vacuum arrangements is important.
The above-noted prior art vacuum apparatus have inadequately, or not at all, addressed the concerns noted above. A need exists in the art for apparatus and methods which address the above concerns.
Other manufacturing processes are known which require movement of a flexible sheet against a product, such as in the case of a membrane press apparatus. In a membrane press apparatus, the product to be manufactured is outside an enclosed chamber formed between a first rigid member and a flexible sheet. The enclosed chamber is pressurized to a pressure greater than atmospheric pressure such that the flexible sheet, sometimes heated, is pressed against the product. Sometimes a vacuum assist may be provided to draw the flexible sheet toward the product. Such an arrangement is useful to manufacture wood laminates, for example, an oak laminate over a chip board.
In a membrane press apparatus, prior to pressurizing the enclosed chamber to a pressure greater than atmospheric pressure, a vacuum is sometimes applied in the enclosed chamber to draw the flexible sheet toward the first member. By heating the first member and drawing the flexible sheet toward the first member, this facilitates more rapid heating of the flexible sheet, and also moves the flexible sheet away from the product. To seal between the flexible sheet and the first member, a solid seal member is provided. A mechanical fastener grips the flexible sheet to attach the sheet to the first member. A seal is formed between the seal member and the flexible sheet through appropriate tension in the flexible sheet and/or pressing the first member and flexible sheet against a rigid work surface.
This type of membrane press arrangement is subject to problems due to the need for the extra mechanical fastener which must properly grip the flexible sheet. Also, the flexible sheet is sometimes subject to failure due to rubbing or chafing of the flexible sheet around sharp corners of the first member. It is clear that a need exists in the art for an apparatus and method which addresses these concerns.